Noisy pulses enhance temporal resolution in pump-probe spectroscopy

TL;DR

This paper introduces noise-enhanced pump-probe spectroscopy, which uses randomly fluctuating light fields to measure quantum dynamics faster than the average pulse duration, surpassing traditional methods in temporal resolution.

Contribution

The paper presents a novel approach leveraging noisy, partially coherent light fields to achieve higher temporal resolution in pump-probe spectroscopy than conventional frequency-stabilized pulses.

Findings

Statistically fluctuating fields outperform stabilized fields by over a factor of 10.

The method enables measurement of dynamics shorter than the average pulse duration.

Application explains recent observation of vibrational wave packet motion in deuterium ions.

Abstract

Time-resolved measurements of quantum dynamics are based on the availability of controlled events (e.g. pump and probe pulses) that are shorter in duration than the typical evolution time scale of the dynamical processes to be observed. Here we introduce the concept of noise-enhanced pump-probe spectroscopy, allowing the measurement of dynamics significantly shorter than the average pulse duration by exploiting randomly varying, partially coherent light fields consisting of bunched colored noise. It is shown that statistically fluctuating fields can be superior by more than a factor of 10 to frequency-stabilized fields, with important implications for time-resolved pump-probe experiments at x-ray free-electron lasers (FELs) and, in general, for measurements at the frontiers of temporal resolution (e.g. attosecond spectroscopy). As an example application, the concept is used to explain the recent experimental observation of vibrational wave packet motion in a deuterium molecular ion on time scales shorter than the average pulse duration.